Does not build on macOS Big Sur

[dagheyman]

Your system information

• Operating system used: macOS 11.0.1
• pyscard version: latest commit from master branch
• Python version: 3.7.3

Please describe your issue in as much detail as possible:

Describe what you expected should happen.

Building pyscard from source on macOS Big Sur fails. Installing from pip fails as well.

Describe what did happen.

$ sw_vers 
ProductName:    macOS
ProductVersion: 11.0.1
BuildVersion:   20B50
$ python3 --version
Python 3.7.3
$ pwd
/Users/d.heyman/code/pyscard
$ make
python3 setup.py build
running build
running build_py
running build_ext
building 'smartcard.scard._scard' extension
swigging smartcard/scard/scard.i to smartcard/scard/scard_wrap.c
swig -python -outdir smartcard/scard -DPCSCLITE -o smartcard/scard/scard_wrap.c smartcard/scard/scard.i
creating build
creating build/temp.macosx-11-x86_64-3.9
creating build/temp.macosx-11-x86_64-3.9/smartcard
creating build/temp.macosx-11-x86_64-3.9/smartcard/scard
clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -DVER_PRODUCTVERSION=2,0,0,0000 -DVER_PRODUCTVERSION_STR=2.0.0 -DPCSCLITE=1 -Ismartcard/scard/ -I/usr/include/PCSC -I/usr/local/include/PCSC -I/usr/local/include -I/usr/local/opt/openssl@1.1/include -I/usr/local/opt/sqlite/include -I/usr/local/opt/tcl-tk/include -I/usr/local/Cellar/python@3.9/3.9.1_7/Frameworks/Python.framework/Versions/3.9/include/python3.9 -c smartcard/scard/helpers.c -o build/temp.macosx-11-x86_64-3.9/smartcard/scard/helpers.o
clang: error: invalid version number in 'MACOSX_DEPLOYMENT_TARGET=11'
error: command '/usr/bin/clang' failed with exit code 1
make: *** [build] Error 1

Steps for reproducing this issue:

1. Install python and swig from homebrew
2. Try to build pyscard

[dagheyman]

Sorry this is something with my environment, not reproducible on other machines.

[LudovicRousseau]

Exact. I can't reproduce the issue either.